1. Field of the Invention
The present invention relates to a fabricating method of an electron source device. More particularly, the present invention relates to a fabricating method of an electron-emitting device.
2. Description of Related Art
A Field Emission Display (FED) that is analogous to a conventional Cathode Ray Tube (CRT) display is a flat panel display technology. The principle of an operation of the FED is briefed as follows. First, with an induction of electric field, a plurality of electron source devices emits electrons from a cathode. Next, electrons are attracted and speeded up by an anode to bombard a phosphor on a surface of the anode so as to emit fluorescence light. After that, the fluorescence passes through the anode and emits from the back side of the anode. Thereafter, the back side of the anode which is on a front side of display panel can show an image.
According to different modes of electron emission, the electron source devices can be classified into a spindt, a Surface Conduction electron-emitting Device (SED), a Carbon Nanotube (CNT), a Ballistic Electron Surface emitting Display (BSD), and so on.
FIG. 1 illustrates a cross-section of a conventional electron-emitting device. Referring to FIG. 1, an electron-emitting device 100 includes a substrate 110, a first electrode 120a, a second electrode 120b and a conductive film 130, wherein the conductive film 130 has a gap G′. However, the width of the gap G′ in the electron-emitting device 100 affects the relationship between a cathode voltage and an emitting current. The following description interprets the relationship among the cathode voltage, the emitting current and the gap G′ width.
FIG. 2 illustrates a curve comparison showing the relationship of the cathode voltage and the emitting current of two kinds of conventional electron-emitting devices. Referring to FIG. 2, horizontal and vertical axes represent the cathode voltage and the emitting current, respectively. A curve 101 shows the characteristic curve about the relationship of the cathode voltage and the emitting current of the electron-emitting device having a gap G′ width of 90 nanometers (nm). A curve 103 shows the characteristic curve about the relationship of the cathode voltage and the emitting current of the electron-emitting device having the gap G′ width of 30 nm.
As shown in FIG. 2, the emitting current in the curve 103 is greater than the emitting current in the curve 101 under the same cathode voltage. That is, compared with the electron-emitting device having the gap G′ width of 90 nm, the electron-emitting device having the gap G′ width of 30 nm can adopt a lower cathode voltage to generate the emitting current. Furthermore, the component characteristic of the electron-emitting device having the gap G′ width of 30 nm is better than the component characteristic of the electron-emitting device having the gap G′ width of 90 nm. Thus, a FED technique is taken up with the development getting a smaller gap width in the electron-emitting device.
However, when the gap G′ width is in a sub-micrometer scale, electrons can not be emitted from the surface of the conductive film 130 by a quantum tunnel effect under an enforced electric field. Thus, an activation process should be done for reducing the gap G′ into a nanometer scale, wherein the better gap G′ width is smaller than 5 nm. In addition, when the gap G′ width is smaller, the electron-emitting device 100 has the better component characteristic. However, it is a precise but difficult to be controlled process for reducing the gap G′ from the sub-micrometer scale into the nanometer scale.